Structure and peculiarities of nanodeformation in Ti–Zr–Ni quasi-crystals

Nanoindentation studies on single crystals of Zn–Mg–Er and Zn–Mg–Ho icosahedral phases

“…It is also important to point out that the values of E and H are close to that of Cubased bulk metallic glasses and Ti-Zr-Ni QCs [34]. However, in case of Al-based QC and Ti-based QC the E is found to be around 200 and 130 GPa, respectively [22][23][24]35]. It can be mentioned that indentation characteristics of single quasicrystals of Zn-Mg-Ho/Er on 5-fold planes are close to that of high quality Ti-Zr-Ni poly-quasicrystalline samples [35,36].…”

“…The frequency of 'pop-ins' suggests that this phenomenon cannot be attributed to the cracking or fracturing of the oxide phases or phase transformation. The discrete change of the 'pop-ins' also suggests that these are due to the elastic-plastic transition and similar to the earlier cases [24,34,37]. It is well known that a QC phase is not a strain hardening material like simple ductile metals and there is no scope for plastic instability like dynamic strain ageing which occurs due to dislocation-precipitate or interstitial atom interaction in alloys.…”

“…Therefore, the displacement burst can be attributed to the deformation in localised regions (similar to bulk metallic glasses) in form of nucleation and propagation of shear bands. In absence of dislocations, the BMG and polycrystalline Ti-Zr-Ni QC have been shown to exhibit this type of behaviour [24,34,35]. It is understood that the dislocations in this QC can be activated at high temperature but not at room temperature.…”

“…Dub et al [19] have investigated the nanoindentation responses of an Al-Cu-Fe QC phase and suggested phase transformation in order to explain 'pop-ins' (basically discontinuities in the load-displacement, F-h curve, also known as serrations or ripples) of the loading curve. However, later they explained their results based on the elastic-plastic transition [24]. Distinct 'popins' effects also have been reported in Al-Ni-Co and Mg-Zn-Y single QC structures [18,22].…”

Bridging room-temperature and high-temperature plasticity in decagonal Al–Ni–Co quasicrystals by micro-thermomechanical testing

“…So far, no agreed conclusion has been reached, and some explanations are: grain-boundary glide rather than a dislocation mechanism [25], pure dislocation climb [15], dominant climb with possible glide [16], phase transformations [26], the nucleation and propagation of shear bands similar to metallic glasses [27]. Still, the plasticity of quasicrystals was poorly explored in a wide range of temperature and pressure -much in contrast to that of crystalline and amorphous solids.…”